The present invention relates to an image sensor; and, more particularly, to an apparatus and method for detecting and correcting defective pixels in an image sensor.
Generally, an image sensor is an apparatus to capture images using light sensing semiconductor materials. Since brightness and wavelength of light from an object are different in their amount according to the reflection area, electrical signals from pixels are different from each other. These electrical signals are converted into digital signals, which can be processed in a digital circuit, by an analog-to-digital converter. Thus, the image sensor needs a pixel array having a plurality of pixels, an analog-to-digital converter for converting analog voltage signals outputted from the pixel array into a digital voltage signals, a plurality of storage devices and so on.
Since the image sensor needs a plurality of devices such as pixels, converters and so on, a possibility of defects therein may always exist in fabricating the image sensor. The defects may occur in a form of spots and lines on a displaying device. Furthermore, if the image sensors having partial defects are considered as a device failure, yield may be dramatically reduced.
It is, therefore, an object of the present invention to provide an apparatus and method for detecting and correcting defective pixels in an image sensor, thereby improving yield of the device.
In accordance with an aspect of the present invention, there is provided a method for detecting and correcting a defective pixel in an image sensor including an M(row line)xc3x97N(column line) unit pixels, the method comprising the steps of: a) electrically scanning photoelectric charges generated from unit pixels of a first row line for a first integration time and storing a first data corresponding to the photoelectric charges; b) electrically scanning photoelectric charges generated from the unit pixels of the first row line for a second integration time and storing a second data corresponding to the photoelectric charges; c) comparing the first data and the second data one another, if the first data is different from the second data, an error signal is generated and then a corresponding address of the unit pixel is stored as a defective pixel address; d) repeating the step a) to the step c) to an Mth line by increasing an address by one; e) comparing an address of a unit pixel to be read with the defective pixel address, if the address of the unit pixel is equal to the defective pixel address, a correction operation is performed to generated a corrected data.
In accordance with another aspect of the present invention, there is provided an apparatus for detecting and correcting a defective pixel in an image sensor having a pixel array, wherein the pixel array includes an M(row line)xc3x97N(column line) unit pixels, comprising: unit pixels, driven by an integration address and a scan address, for receiving a first and second integration time and a critical value in response to an enable signal at a defective pixel detection mode to generate a first data and a second data from respective unit pixels corresponding to the integration address and the scan address according to the first and second integration time, respectively; a defective pixel detection means for comparing a critical value with a difference between a first data and a second data to generate an error signal in case where the difference is smaller than the critical value, and to output the integration address, the scan address and the column address of corresponding unit pixel; a defective pixel address storage means for storing the defective pixel address in response to the error signal and comparing the integration address, the scan address and the column address with the defective pixel address to generate a defective pixel defection signal; and a defective pixel correction means for correcting the first data and the second data of the defective pixel in response to the defective pixel detection signal to generate a first corrected data and a second corrected data, respectively.